• Food Science and Biotechnology
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• v.18 no.2
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• pp.526-532
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• 2009

Quenching mechanisms and kinetics of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol in photosensitized oxidation of lard were studied. Lard at 0.03, 0.07, 0.11, and 0.3 M in methylene chloride containing $4.4{\times}10^{-6}\;M$ chlorophyll and 0, 0.1, 0.3, and 0.6 mM $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol were stored under light for 4 hr, respectively. Oxidation was determined by headspace oxygen and peroxide value. Tocopherols prevented the photosensitized oxidation of lard (p<0.05). Steady state kinetic study showed that $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol prevented the photosensitized oxidation of lard by quenching singlet oxygen. Singlet oxygen quenching rates of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol by headspace oxygen depletion were 1.86, 2.39, 2.47, and $2.11{\times}10^7/M/sec$, respectively. The quenching rates of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol by peroxide value were 1.42, 1.11, 0.97, and $0.42{\times}10^7/M/sec$, respectively. The quenching rates of tocopherols were slightly different depending on the measurements of oxidation.

• Bulletin of the Korean Chemical Society
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• v.22 no.1
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• pp.63-67
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• 2001

The photophysical properties and the singlet oxygen generation efficiency of tetrathiarubyrin have been investigated to elucidate the possibility of its use as a photodynamic therapy (PDT) photosensitizer by steady-state and time-resolved spectroscopic methods. The observed photophysical properties were affected by various molecular aspects, such as extended ${\pi}conjugation$, structural distortion, and internal heavy atom. The steady-state electronic absorption spectrum was red-shifted due to the extended $\pi-conjugation$, and the spin orbital coupling was enhanced by the structural distortion and the internal heavy atom effect. As a result of the enhanced spin orbital coupling, the triplet quantum yield increased to 0.90 $\pm$ 0.10 and the triplet state lifetime was shortened to 7.0 $\pm$ 1.2 ${\mu}s$. Since the triplet state decays at a relatively faster rate, the efficiency of the oxygen quenching of the triplet state decreases. The singlet oxygen quantum yield was estimated to be 0.52 $\pm$ 0.02, which is somewhat lower than expected. On the other hand, the efficiency of singlet oxygen generation during the oxygen quenching of triplet state, $f{\Delta}^T$, is near unity. Such high efficiency of singlet oxygen generation can be explained by the following two possible factors: The hydrogen bonding of ethanol which impedes the deactivation pathway of the charge transfer complex with oxygen to the ground state, the less probability of the aggregation formation.

• Journal of Photoscience
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• v.11 no.32
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• pp.77-81
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• 2004

Deoxygadusol (DO) and structurally related mycosporine-like amino acids, i.e. mycosporine glycine (MO) and mycosporine taurine (MT), were isolated from phytoplankton Prorocentrum micans and studied for the reactivity toward singlet oxygen. These water-soluble compounds with a cyclohexenone chromophore were all shown to be highly effective in quenching singlet oxygen ($^1$ $O_2$), with the efficiencies being significantly larger compared with histidine, a well-known $^1$ $O_2$ quencher. The $^1$ $O_2$ reaction rate constant ( $k_{Q}$) of DG was determined to be 5.4 ${\times}$ 10$^{7}$ $M^{-1}$ $s^{-1}$ by a steady state method based on competitive inhibition of rubrene oxidation. The feasibility of this method was confirmed by estimating the $k_{Q}$ values for MG and two other quenchers, furfuryl alcohol and 1,4-diazabicyclo [2,2,2]octane, and comparing with those values determined by the time-resolved $^1$ $O_2$ decay method in the previous work.ork.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.13 no.1
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• pp.45-71
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• 1987

${\beta}$-Carotene has been known as an effective quenching agent of singlet oxygen and the carotenoid pigments in general are expected to protect cells against photosensitized oxidations. We are determined the quenching rate constants of several Ketocarotenoids including capsanthin, capsanthin diester, astaxanthin and fucoxanthin, and the relative quenching actiyities against singlet oxygen were compared with those of ${\beta}$-carotene and reported carotenoids. Nevertheless the ketocarotenoids exhibited lower quenching rate constants than ${\beta}$-carotene, they showed more pronounced protective activitives than ${\beta}$-carotene against photohemlysis induced by singlet oxygen. Among the ketocarotenoids investigated, fucoxanthin indicated a significant protective activity for the cell. The results suggested that. 1) 1O2 may be alikely initiator of photohemolysis, but this reaction is followed by slow dark reactions involving secondary reactive species. 2) For protection of RBC against photodynamic action with carotenoids, carotenoids having functional groups such as -C=0 and -OH groups are most efficient. This suggests that partition of carotenoids between the buck and the mombrane and/or their specific binding to membrane proteins are more critical for the photo-protection by carotenoids than is a diffusional quenching of 1O2.

• Journal of Photoscience
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• v.9 no.2
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• pp.63-65
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• 2002

This report concerns a putative role of mycosporine-like amino acids (MAA) as natural scavengers of singlet oxygen ($^1$O$_2$) in marine organisms. MAA prepared from the ascidian Lissoclinum patella were found to protect biological systems against detrimental effects of the type II photosensitization in vitro. L. patella MAA were resolved into five components, and the relative $^1$0$_2$ quenching efficiencies were measured for three major components in aqueous media. It turned out that they were all effective in scavenging $^1$0$_2$, to different degrees albeit. The results suggest that physiological relevance of MAA in marine organisms may be found in a 'built-in' defense against photooxidative effects of sunlight.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.3102-3102
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• 2001

Constituents of several .representative seaweeds, such as wakame Undaria pinnatifida; hijikia Hizikia fusifome; and kombu Laminaria japonica, were found to have fairly large reaction rates determined by quenching experiments of emission spectra in the near-infrared region (1max: 1270 nm) from singlet oxygen (102). Emission spectra of singlet oxygen generated from an aqueous solution of Rose Bengal under irradiation with a green laser (330 nm) were measured by a near-infrared (NIR) emission spectrometer constructed in our laboratory. The quenching experiments were as follows: Intensities of emission spectra were measured in the absence (I0) and in the presence of the seaweed constituents (I): Ratios of I0/I were plotted against every concentration of the quenchers (Stern-Volmer plots) which gives a straight line. The slope of each line gives a kqt value which gives a quenching constant kq value (an antioxidative constant against singlet oxygen) when the t value (half-life time of singlet oxygen in the solvent used) was given. The determined reaction rates are between 103-105 (g/l)-ls-1; the larger ones are as large as that of ascorbic acid, 8.4 ${\times}$ 104 (g/1)-ls-1. Most of these seaweed constituents also showed antioxidative activity against auto-oxidation and superoxide as well as their immunological enhancing activity. These results suggest a possibility that dietary fibers which are supposed to prevent the large-intestine cancer by their physical properties may prevent the cancer, at least in parts, by their chemical, antioxidative activity.

• Rapid Communication in Photoscience
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• v.3 no.4
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• pp.81-84
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• 2014

To examine the microenvironmental effect of DNA on the photosensitized reaction, the electron-donor-connecting porphyrin, meso-(9-phenanthryl)-tris(N-methyl-p-pyridinio) porphyrin (Phen-TMPyP), was synthesized. Phen-TMPyP can bind to oligonucleotides with two binding modes, depending on the DNA concentration. The fluorescence lifetime measurement of Phen-TMPyP shows a shorter component than that of the reference porphyrin without the phenanthryl moiety. However, the observed value is much longer than those of previously reported similar types of electron-donor-connecting porphyrins, suggesting that electron-transfer quenching by the phenanthryl moiety is not sufficient. The fluorescence quantum yield of Phen-TMPyP ($5{\mu}M$) decreased with an increase in DNA concentration of up to $5{\mu}M$ base pair (bp), possibly due to self-quenching through an aggregation along the DNA strand, increased with an increase in DNA concentration of more than $5{\mu}M$ bp and reached a plateau. The fluorescence quantum yield of Phen-TMPyP with a sufficient concentration of DNA was larger than that of the reference porphyrin. The singlet oxygen ($^1O_2$) generating activity of Phen-TMPyP was confirmed by the near-infrared emission spectrum measurement. The quantum yield of $^1O_2$ generation was decreased by a relatively small concentration of DNA, possibly due to the aggregation of Phen-TMPyP, and recovered with a sufficient concentration of DNA. The recovered quantum yield was rather smaller than that without DNA, indicating the quenching of $^1O_2$ by DNA. These results show that a DNA strand can stabilize the photoexcited state of a photosensitizer and, in a certain case, suppresses the $^1O_2$ generation.

• Rapid Communication in Photoscience
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• v.4 no.2
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• pp.37-40
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• 2015

To examine the photosensitized biomolecules damaging activity, dimethoxyP(V)tetrakis(2-naphthyl)porphyrin (NP) and dimethoxyP(V)tetraphenylporphyrin (PP) were synthesized. The naphthyl moiety of NP hardly deactivated the photoexcited P(V)porphyrin ring in ethanol. In aqueous solution, the naphthyl moiety showed the quenching effect on the photoexcited porphyrin ring, possibly through electron transfer and self-quenching by a molecular association. Binding interaction between human serum albumin (HSA), a water soluble protein, and these porphyrins could be confirmed by the absorption spectral change. The apparent association constant of NP was larger than that of PP. It is explained by that more hydrophobic NP can easily bind into the hydrophobic pockets of HSA. The photoexcited PP effectively induced damage of the tryptophan residue of HSA, through electron transfer-mediated oxidation and singlet oxygen generation. NP also induced HSA damage during photo-irradiation and the contributions of the electron transfer and singlet oxygen mechanisms were speculated. The electron transfer-mediated mechanism to the photosensitized protein damage should be advantageous for photodynamic therapy in hypoxic condition. The quantum yield of the HSA photodamage by PP was significantly larger than that of NP. The quenching effect of the naphthyl moiety is considered to suppress the photosensitized protein damage. In conclusion, the naphthalene substitution to the P(V)porphyrins can enhance the binding interaction with hydrophobic biomacromolecules such as protein, however, this substitution may reduce the photodynamic effect of P(V)porphyrin ring in aqueous media.

• Food Science and Preservation
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• v.23 no.3
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• pp.387-392
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• 2016

The antioxidant activities of brownish natural dyeing agents, extracted from seven kinds of plants, were tested. Total polyphenol content, DPPH and ABTS radical scavenging activities, and singlet oxygen quenching effect were determined for hot water extracts and floral waters of plants. DPPH and ABTS radical scavenging activites increased with increasing amounts of the extracts from Uncaria gambir R. and Terminalia chebula R. displayed remarkable scavenging effects at concentrations below 0.1 mg/mL, in comparison with the positive control, ascorbic acid. However, antioxidant effects of the floral water, obtained from steam distillation of tested plants, were inefficient at concentration below 0.2 mg/mL. In particular, the natural dyeing agent effectively suppressed singlet oxygen induced by photosensitizer in in vitro assay systems. The concentrations ($IC_{50}$) required to exert 50% of singlet oxygen were 120 and $190{\mu}g/mL$ for hot water extracts from Uncaria gambir R. and Phellinus linteus, respectively. Among all the tested samples, the Uncaria gambir R. and Phellinus linteus extracts contained higher amount of total phenolic contents. The results suggest that naturally occurring dyeing agents are beneficial as natural antioxidants, encouraging further extensive studies.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1608-1612
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• 2012

Singlet oxygen ($^1O_2$) is an important species for oxidation in biological processes. $^1O_2$ is implicated in the genotoxic effect, and plays an important role in the cell-signaling cascade and in the induction of gene expression. However, the rapid detection of $^1O_2$ in biological environments with sufficient specificity and sensitivity is hampered by its extremely low emission probability. Here, a layer-by-layer (LbL) film of CdTe quantum dots (QDs), polymers, and ascorbate have been designed as a rapid, highly selective, and sensitive fluorescence probe for $^1O_2$ detection. Upon reaction with $^1O_2$, the probe exhibits a strong photoluminescence (PL) response even at trace levels. This remarkable PL change should enable the probe to be used for $^1O_2$ detection in many chemical and biological systems and as an environmental sensor.